Ah that vaguly looks familar (high school was a long time ago). Now I don't think it can be applied to this series as part of the definition says "where no two xj are the same." Or am I misssing something?

Yes, you are missing something :-)
In this case, the x's are 1,2,3,4,5,...,n and the y's are 2,2,2,3,7,...m
And the method gives a function f so that f(1) = 2, f(2) = 2, f(3) = 2, f(4) = 3, and so on...

When putting a smiley right before a closing parenthesis, do you:

Use two parentheses: (Like this: :) )
Use one parenthesis: (Like this: :)
Reverse direction of the smiley: (Like this: (: )
Use angle/square brackets instead of parentheses
Use C-style commenting to set the smiley off from the closing parenthesis
Make the smiley a dunce: (:>
I disapprove of emoticons
Other